The BBC’s Home Affairs Correspondent Danny Shaw said it is unknown at this stage whether the victim and the suspect were known to each other.
A woman is thought to have been beheaded in the garden of a north London house.
The victim was found at an address in Nightingale Road, Edmonton, at about 13:00 BST, police said.
Officers discovered her collapsed in a garden area and she was pronounced dead at the scene.
A 25-year-old man was arrested on suspicion of murder and is in custody. Detectives said there is no suggestion the killing had a terrorist motive.
A Taser was used during the arrest of the man and a firearms officer is believed to have suffered a broken wrist.
‘Visible attack’
Police said the woman’s next of kin had not been informed so they were unwilling to speculate on the nature of the woman’s injuries or the type of weapon used.
Det Ch Insp John Sandlin said: “This is was a highly visible attack in broad daylight on a residential street.
“I can understand why this may cause people concern, however we are confident that we are not looking for anyone else at this stage.
“Whilst it is too early to speculate on what the motive behind this attack was I am confident, based on the information currently available to me, that it is not terrorist related.
“Specially trained family liaison officers will be deployed to support the family.”
He added officers and specialist detectives would be on the scene for many hours to come.
London Ambulance Service said they sent a number of resources to the scene including London’s Air Ambulance, an ambulance crew and a duty manager.
The BBC’s Home Affairs Correspondent Danny Shaw said it is unknown at this stage whether the victim and the suspect were known to each other.
The case is being investigated by Scotland Yard’s Homicide Command.
